APU Flashcards
According to the SOPM, when should the APU be turned on?
10 minutes prior to pushback
What electrical requirements are there for the APU?
If AC external is not available batteries 1 & 2 must be on DC GPU may replace Batt 2 but not Batt1
ECS ON, APU ___
Off
ECS OFF, APU ___.
On
Recite APU Starter Duty Cycle Limits
1 & 2 60s OFF, 3rd Attempt 5 min OFF
APU Limitations
33,000 for use.
30,000 to start.
21,000 to start the engine with APU bleed air.
15,000 to power PACKS with APU bleed air
What do the APU switches do?
OFF: Initiates shutdown sequence, APU bleed closes immediately, after 1 min fuel, FADEC and GEN power is off
ON: Powers FADEC and opens APU fuel shutoff valve wait 30s to start
START: Initiates start sequence (momentary position)… 3 seconds after APU has reached 95% power and air are avail
Where does the APU receive fuel from? Which pumps?
The right fuel tank.
When only DC power is available then the DC fuel pump
AC fuel pump if we have AC power
Ejector fuel pump if engine is running (can Xfeed from another engine)
When will the APU automatically turn off? In flight? On the ground?
UFO/SHELF on Ground, UFO in flight
How do I shut the APU off? Is there a cooldown period? What happens during the cooldown period? Can the cooldown period be canceled systematically? Operationally? Can I turn the APU back ON during the cooldown period? Spool Down period?
Switching knob to OFF closes APU bleeds immediately and there is a one minute cooldown. APU slows and cools down. You can turn it back on during the 1 minute cooldown. After the 1 minute period you must re do the start sequence
What is the APU shutdown procedure when powering down the aircraft?
Make sure APU indication is off and wait an additional 80 seconds to receive an APU FUEL SOV CLOSED EICAS message before turning off the batteries. Failure to do so can cause an APU Fault
